An insulated gate bipolar transistor (IGBT) is a composite full-controlled voltage-driven power semiconductor component composed of a bipolar junction transistor (full name: Bipolar Junction Transistor, briefed as BJT) and a metal-oxide-semiconductor-field effect transistor (Metal-Oxide-Semiconductor Field-Effect Transistor, MOSFET).
In a conventional IGBT structure, there are two opposite primary surfaces, namely, a first primary surface and a second primary surface. The first primary surface is a front surface of a chip, and includes a cell region and a terminal region; and the second primary surface is a back surface of the chip, includes an IGBT collector region, and in addition, also includes an IGBT drift region.
FIG. 1 is a top view of a conventional IGBT structure, that is, a schematic diagram of a front surface of a chip, including a cell region 100 and a terminal region 200, where the terminal region 200 completely surrounds the cell region 100, implementing a function of electric field voltage division of a chip plane. FIG. 2 is a cross-sectional diagram of FIG. 1 along an A-A line. As shown in FIG. 2, the cell region 100 includes a gate 101, an emitter 102, a p well region 103, an n+ emitter region 104 and a p+ emitter region 105 which are contained in the p well region 103 and contact the emitter, a gate region 107, a gate oxidation region 106, and an oxide isolation layer region 206. Multiple gate regions 107 are connected together by using metal to form the gate 101 of the IGBT. The p well region 103, and the n+ emitter region 104 and the p+ emitter region 105 which are contained in the p well region 103, are connected together by using metal to form the emitter 102 of the IGBT. The terminal region 200 includes a first field ring p region 201, several field ring p regions 202, a p+ region 204 connected to the emitter 102, a field plate region 205, an equipotential ring n region 203 at an edge of the chip, and an oxide isolation layer region 206.
As shown in FIG. 2, the back surface of the chip includes an IGBT collector region 301 and a collector metalization region 300, where the IGBT collector region 301 is p+. The collector metalization region 300, the gate 101, and the emitter 102 form three electrode ports of the IGBT.
In addition, as shown in FIG. 2, a first drift region 108 is under the cell region 100, and a second drift region 207 is under the terminal region 200. The first drift region 108 and the second drift region 207 are jointly called an IGBT drift region, where the IGBT drift region is n−.
The IGBT is a large power switching component, with key features of switching feature parameters and high reliability. Generally, when the IGBT is forward conductive, a positive gate voltage makes a channel formed, and electrons of the emitter flows to the drift region via the channel. Due to requirements of forward bias and electric neutrality of the collector, a large number of holes are injected from the collector to the drift region, and form conductivity modulation with electrons in the drift region. Because of the conductivity modulation effect when the IGBT is forward conductive, the IGBT has advantages of a low forward conduction voltage drop, a large on-state current, and low loss.
However, when the IGBT is turned off, and after the gate voltage is reduced to be smaller than a threshold voltage, the channel is cut off, and an electron current of the emitter turns to zero. In circumstances of widely applied inductive loads, because an inductive current cannot be suddenly changed, which means that a current flowing through the IGBT cannot be changed suddenly, all currents flowing through the IGBT must be provided by a hole current formed by the holes injected from the collector to the drift region. In this case, for the terminal region of the IGBT component, a large number of holes are injected from the collector of the component to the drift region. However, the injected holes cannot be directly pumped out from a floating field ring structure of the terminal, but gather at the equipotential ring of the terminal, resulting in a longer hole recombination time, a lower turn-off speed, and greater turn-off loss. In addition, a local gathering effect of the hole current is formed at the equipotential ring of the terminal, which causes a high voltage and a strong current and makes a component temperature rise rapidly, resulting in dynamic avalanche breakdown and thermal breakdown of the component and burning of the component.